Larger data processing systems typically include a plurality of host processors and typically require storage for large numbers of data storage media. The data storage media are typically optical disks or magnetic tapes which are stored in a library having a plurality of storage slots, and which can be accessed by a picker. The storage slots may be arranged in rows, and the rows are arranged in columns. The conventional picker is a robotic device which moves along a guideway in a horizontal motion, or about a pivot in a rotary motion, and moves vertically to access the various storage slots. Commands received from the host(s) are often queued to permit the receipt of additional commands during the execution of the previous command so that the processing speed of the system is increased. Additionally, two pickers may be provided and may be operated simultaneously to increase the speed of the system. An example of a library having queuing and two pickers is illustrated in U.S. Pat. No. 5,513,156, Hanaoka et al., issued Apr. 4, 1996.
The difficulty is that each of the pickers is limited to access only one section of the library at the same time, and no picker is allowed to access the same storage slot as another picker. Thus, if all of the required data storage media is stored in one section of the library, only one picker may be utilized to access the media at a time. The reason for the limitation is the probability of interference between the pickers. An added complication results if the pickers are wider than a single column, requiring a separation or added clearance between the two fixed sections of the library.